Method and device for processing signals

ABSTRACT

A method is set forth for processing signals, in particular for treating audio signal, characterized in that it mainly consists in the supply of an input signal (3) to be treated; in the isolation of a number of signals (5) from the input signal (3) which are mainly situated in a predetermined part of the sound range; in the additional generation of higher harmonics on the basis of the isolated signals (5); and in the formation of an output signal (9) by combining the signal (7) which contains the generated higher harmonics with at least part of the above-mentioned input signal (3), this input signal (3) is either treat or not treated before being combined.

FIELD OF THE INVENTION

The present invention concerns a method and device for processingsignals.

In particular, it concerns a method and device for processing audiosignals, particularly in order to improve the sound quality and/or tocreate special effects.

BACKGROUND OF THE INVENTION

It is known that audio signals can be subject to different types ofinterferences. An important type of interference hereby is noise.Moreover, various other types of interferences may occur such asdistortions which have a negative effect on the sound clarity.

SUMMARY OF THE INVENTION

The present invention concerns a method and device for processingsignals which makes it possible to significantly improve the soundquality of audio signals, irrespective of the source of the signal to beimproved.

To this end, the invention concerns a method for processing signals, inparticular for treating audio signals, characterized in that it mainlyconsists in the supply of an input signal to be treated; in theisolation of a number of signals from the input signal which are mainlysituated in a predetermined part of the sound range; in the additionalgeneration of higher harmonics on the basis of the isolated signals; andin the formation of an output signal by combining the generated higherharmonics with at least part of the above-mentioned input signal,whereby this input signal was treated or not treated before beingcombined.

According to a preferred embodiment, in order to produce the isolatedsignal, on the basis of which the higher harmonics are generated, thetones which exceed a certain value are isolated and transmitted. Thepass limit, in other words the frequency for which the tones are allowedto pass, is preferably situated between 3,000 and 5,000 Hz, and betterstill at about 3,500 Hz.

Moreover, it is preferable that only those tones which are situatedunder a certain value are isolated, in other words that the tones whichare situated above this value are eliminated or at least considerablyabated. The pass limit, in this case the limit above which the tones areeliminated or considerably abated, is preferably situated between 4,000and 19,000 Hz and better still at about 7,000 Hz.

According to a special embodiment of the method according to theinvention, the input signal is treated before being combined with thesignal which consists of the additionally generated higher harmonics.This treatment may consist in that the tones within a certain range alsoeliminated and/or abated. Preferably, only tones below a certain passlimit are let through, whereby this pass limit is preferably situated atabout 7,000 Hz.

Also, according to the most preferred embodiment, the higher harmonicsare generated on the basis of the signals of only a restricted band ofthe sound range, namely those included between 3,500 and 7,000 Hz.

The combination of the signal which produces the additionally generatedhigher harmonics with the input signal which was either treat or nottreated, in order to provide for the above-mentioned end signal, ispreferably realized by supplying both signals to an adder amplifier.

According to yet another special embodiment, in order to optimize theaimed effect, an additional control is preferably provided, thisadditional control consists in that the passage of the additional higherharmonics is regulated as a function of the input signal, or at least asa function of the intensity of this input signal. This controlpreferably makes it possible for the signal of the additionallygenerated higher harmonics to be more or less amplified as a function ofthe input signal.

Depending on the desired effect, different methods can be used with thiscontrol. Preferably, the input signal, or at least part thereof, istransformed into a control signal which provides a requiredamplification for the signal with the additionally generated higherharmonics. This control signal can be obtained by rectifying theabove-mentioned input signal, or a part thereof, and subsequentlytransforming it into a typical control signal for an amplifier.

The above-mentioned transformation may be carried out according to amathematical function. Preferably, a linear transformation is providedfor.

The above-mentioned control signal does not necessarily have to be basedon the entire input signal. Preferably, this control signal is evenderived from merely a part of the input signal, such as a part situatedwithin a certain range. Preferably, the control signal is derived and/orcalculated as a function of the full package of higher tones present inthe input signal to be treated, such as the tones above a certain passlimit, preferably situated between 6,000 and 8,000 Hz, and better stillat 7,000 Hz. The present invention also concerns a device to realize theabove-mentioned method.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

In order to better explain the characteristics according to theinvention, the following preferred embodiments of the invention, inparticular of devices according to the invention, are given as anexample only without being limitative in any way, with reference to theaccompanying figures, where:

FIG. 1 represents a device according to the invention in a blockdiagram;

FIG. 2 represents another device according to the invention in a blockdiagram;

FIG. 3 represents a diagram which is related to the operation of thedevice in FIG. 2.

DESCRIPTION OF THE INVENTION

As represented in FIG. 1, the invention concerns a device 1 forprocessing audio signals, in particular for improving and/or alteringthe quality of the sound which results from such signals.

As is also represented in FIG. 1, the device mainly consists of an entry2 for the supply of an input signal 3 to be improved and/or altered;means 4 to isolate a number of signals 5 from the input signal 3 whichare mainly situated in a specific part of the sound range; means 6 forthe additional generation of higher harmonics on the basis of theisolated signals 5, hereafter called signal 7; and means 8 for theformation of an output signal 9 which provide for the combination of thegenerated higher harmonics, in other words the signal 7, with a signal10 which is either identical to the input signal 3, or, as will bedescribed hereafter, forms part of the signal 2, provide or not in afurther treated shape.

The means 4 to isolate a number of signals 5 which are mainly situatedin a specific part of the sound range from the input signal 3, consistof a selective element 11 which lets tones within a certain range passand which eliminates or at least abates the other tones. In preference,a selective circuit is used to this end which eliminates and/or abatesat least the lower tones and lets the higher tones pass or lets thempass for the main part, such as for example a high-pass filter or anadjustable selective filter.

In order to obtain an even better effect, the selective element 11 isnot only made such that only the lower tones under a certain first passlimit are eliminated and/or abated, but also the higher tones above asecond pass limit, whose cutting-off frequency is higher than that ofthe first pass limit, are eliminated and/or abated.

The values of the above-mentioned pass limits will be further elucidatedin the description of FIGS. 2 and 3.

The means 6 for the additional generation of higher harmonics on thebasis of the isolated signals 5 may consist of a harmonics such asdescribed in Belgian patent No. 1004054.

The above-mentioned means 8 for the formation of the output signal 9 onthe basis of the above-mentioned signals 7 and 10 may be of a differentnature. In the example given in FIG. 1, they merely consist of acoupling between the input 2 and the output of the means 6, whichimplies that the signal 7 is superposed on the input signal 3, whichsubsequently results in the above-mentioned output signal 9.

FIG. 2 represents a further developed embodiment.

The above-mentioned means 4 consist in this case of two elements ofelectronic parts 12 and 13.

The element 12 consists of a circuit which eliminates and/or abates thetones under a certain pass limit F1, such as a high-pass filter. Thevalue F1 is preferably situated between 3,000 and 5,000 Hz. Inparticular, this value F1 preferably amounts to 3,500 Hz, as representedby means of the curve A in FIG. 3. This curve A shows that most tones inthe higher range are allowed to pass.

The element 13 consists of a circuit which eliminates and/or abates thetones above a certain pass limit F2, such as a low-pass filter. Thevalue F2 is preferably situated between 6,000 and 19,000 Hz. Inparticular, this value F2 preferably amounts to 7,000 Hz, as representedby means of the curve B in FIG. 3. This curve B shows that tones in thelower range are mostly allowed to pass.

The above-mentioned means 6 are of the same nature as in FIG. 1.

In the embodiment of FIG. 2, the means 8 consist of an adder amplifier.

As already described in the elucidation of the method, the input signal3 can be treated first before being supplied, in the shape of a signal10, to the means 8, in this case the adder amplifier. The treatmentpreferably consists in that only certain tones are allowed to pass.

In order to reach optimum results with the improvement of existingsignals, a circuit is used to this end which eliminates and/or abatesthe tones above a certain pass limit F3, such as a low-pass filter. Thepass limit F3 is preferably situated at 7,000 Hz. In the examplerepresented in FIG. 2, no separate circuit is used to this end, but theelement 13 of the device is also used to this end.

In order to further optimize the aimed effect, the device 1 ispreferably also provided with an additional control 14, which regulatesthe transmission of the additionally generated higher harmonics or inother words the signal 7 as a function of certain characteristics of theinput signal 3. Preferably, the control 14 makes sure that the signal 7is amplified to a greater or lesser extent, as a function of thesupplied input signal 3 or as a function of a part of this signal,whereby the general intensity of the input signal 3 or of theabove-mentioned part thereof is used as a measure for the amplification.

Also, the control 14 mainly consists of a conversion circuit 15 and anadjustable amplifier 16, whereby the amplifier 16 provides for theamplification of the above-mentioned signal 7 and whereby the conversioncircuit 15 delivers a control signal 17 which provides for the controlof the amplifier 16.

The conversion circuit 15 preferably consists of a rectifier 18 and atransformation circuit 19. The transformation circuit 19 in its turnpreferably consists of a linear transformer connection. However, thetransformation circuit 19 may also consist of another connection whichprovides for a transformation according to a mathematical functiondetermined by the designer. According to yet another special embodiment,the transformation circuit 19 is equipped with a threshold connection.

In order to further optimize the aimed effect, only part of the inputsignal 3 is transmitted to the conversion circuit 15 by making use of aselective element 20 which lets through only the tones above a certainpass limit. This pass limit preferably has a value between about 6,000and 8,000 Hz, and better still of 7,000 Hz. Use can be made to this endof a high-pass filter. The working of the selective element 20 isrepresented in FIG. 3 by means of a curve C.

The above-mentioned part 13 and the selective element 20 may possibly beintegrated in one adjustable filter 21.

According to yet another variant, a circuit 22 can be provided toshort-circuit the above-mentioned element 13, such that this element 13,if required, can be switched off.

The working of the device 1 can be easily derived from FIG. 2 and theprevious description.

The original audio signal is supplied as input signal 3 to the input ofthe device 1. This input signal is stripped of part of the top harmonicsthrough the selective operation of the element 13 of the device 1. Theresulting signal is led to the element 12, which, as mentioned above,preferably consists of a high-pass filter, which lets part of theremaining harmonics through.

The remaining signal is supplied to the harmonic generator 6, which addshigh harmonics to the signal.

The obtained signal 7 is supplied to the adjustable amplifier 16 whichin turn transmits an amplified signal to the second input of the adderamplifier 8.

The control voltage of the adjustable amplifier 16 is derived from theinput signal 3. To this end, this input signal 3 is supplied to theselective element 20, in this case a high-pass filter which determineswhether there are any harmonic components as of the set frequency andtransmits them to the conversion circuit 15 which delivers a controlsignal 17 in the shape of an output voltage as a function of the signalafter the rectifier 18, whereby different settings are possible. Asmentioned above, a threshold voltage can hereby be set, but also otherlinear, non-linear and complex relations between the input signal andthe output signal of the transformation circuit 19 are possible, such tomake an optimum acoustic setting possible.

Thanks to the device 1, the noise of the audio signal is less disturbingand/or the sound is broadened in the audible spectrum.

It should be noted that the method as well as the device 1 reduce thesignal/noise relation of audio signals, irrespective of the type ofsource. Taking into account the psycho-acoustic data, the sound isbrightened, in particular provided with extra dominant tones.

It is clear that in this description, by "tones" should usually beunderstood the electric signals corresponding to these tones.

The device 1 can be made in analog form as well as digital.

The present invention is by no means limited to the embodimentsdescribed by way of example and represented in the figures; on thecontrary, such a method and device for processing signals can be made inall sorts of variants while still remaining within the scope of theinvention as defined in the accompanying claims.

We claim:
 1. A method for processing audio signals to adjust quality ofsounds produced comprising:(a) supplying input signals to be treated;(b) isolating a set of basis signals from said input signals, said setof basis signals lying exclusively within at least one frequency range;(c) generating higher harmonic signals representative of higherharmonics of said set of basis signals; and (d) forming output signalsby combining the higher harmonic signals with at least part of saidinput signals, wherein said step of combining the generated higherharmonic signals with at least part of said input signals is controlledat least as a function of signals extracted from said input signals,said extracted signals lying at least in part within a frequency rangeoutside said at least one frequency range.
 2. A method according toclaim 1, wherein said isolated set of basis signals are pass filtered ina first predetermined range such that signals above a given limit canpass before generating said higher harmonics.
 3. A method according toclaim 2, wherein said first predetermined range has a lower value ofbetween 3000 and 5000 Hz.
 4. A method according to claim 3, wherein saidlower value is 3500 Hz.
 5. A method according to claim 2, wherein saidisolated set of basis signals, before or after being isolated, are alsopass filtered in a second predetermined range different from said firstpredetermined range, said first and second predetermined rangespartially overlapping; and wherein isolated signals above a given valueare eliminated or at least abated.
 6. A method according to claim 5,wherein said given value is between 4000 and 19000 Hz.
 7. A methodaccording to claim 6, wherein said given value is 7000 Hz.
 8. A methodaccording to claim 1, wherein at least a part of said input signals arechanged before being combined with said generated higher harmonicsignals to form said output signals, the change including eliminatingpart of said input signals within a selected range.
 9. A methodaccording to claim 8, wherein said change includes pass filtering saidinput signals only below a given limit.
 10. A method according to claim9, wherein said given limit is about 7000 Hz.
 11. A method according toclaim 6, wherein at least a part of said input signals are changedbefore being combined with said generated higher harmonic signals toform said output signals, the change including eliminating part of saidinput signals within a selected range, wherein said change includes passfiltering said input signals only below a given limit, and wherein saidgiven limit is the same value as said given value of said secondpredetermined range.
 12. A method according to claim 1, wherein the stepof combining the generated higher harmonic signals with at least part ofsaid input signals is controlled by amplifying said generated higherharmonic signals as a function of said extracted signals.
 13. A methodaccording to claim 1, wherein the step of combining the generated higherharmonic signals with at least part of said input signals is carried outby forming a control signal from at least a part of said extractedsignals, by rectifying said at least part of said extracted signals, andsubsequently by transforming said at least part of said extractedsignals into said control signal.
 14. A method according to claim 13,wherein said step of transforming said at least part of said extractedsignals is carried out by a predetermined mathematical function.
 15. Amethod according to claim 13, wherein said step of transforming said atleast part of said extracted signals is carried out by a lineartransformation.
 16. A method according to claim 1, wherein said at leastpart of said extracted signals for achieving control of said step ofcombining is formed by pass filtering said at least part of said inputsignals above a given limit.
 17. A method according to claim 16, whereinsaid given limit is about 7000 Hz.
 18. A method according to claim 1,wherein all of said input signals are combined with said generatedhigher harmonic signals to form said output signal.
 19. A device forprocessing audio signals to adjust quality of sounds producedcomprising:(a) means for supplying input signals to be treated; (b)means for isolating a set of basis signals from said input signals, saidset of basis signals lying exclusively within at least one frequencyrange; (c) means for generating higher harmonics of said set of signals;and (d) means for forming output signals by combining the higherharmonic signals with at least part of said input signals, wherein saidmeans for forming output signals by combining the higher harmonicsignals with at least part of said input signals includes means forcontrolling formation of the output signals at least as a function ofsignals extracted from said input signals, said extracted signals lyingat least in part within a frequency range outside said at least onefrequency range.